The global solar industry is volatile, but it grows significantly every year. It's quick to adapt to changing markets, technologies and trade obstacles. The prospect of solar becoming a 100-gigawatt-per-year market is not a matter of "if" but "when."

However, if the IPCC’s latest assessment of widespread economic damage from climate change is correct and humanity is hoping to make a dent in decarbonizing its energy mix, then solar and renewables have to be installed on a much bigger scale. Replacing the thousands of gigawatts of coal- and gas-burning plants on this planet will require many thousands of projects at the scale of say, the 550-megawatt Topaz PV farm or the 290-megawatt Agua Caliente PV plant.

So, if the aim is to grow big and fast, it makes sense to imagine huge multi-gigawatt projects that address the scale problem head-on with really big centralized solar.

Here are three proposed (or perpetually proposed) monster solar projects that align with this vision.

4 Gigawatts From India's Ultra Mega Solar Power Project

Image: India's Sambhar Salt Lake

Five acronymic Indian entities (BHEL, SECL, SSL, POWERGRID, SJVN and REIL) recently signed an "historic" memorandum of understanding to build a 4,000-megawatt solar power plant in India's state of Rajasthan near Jaipur, close to the briny Sambhar Salt Lake.

The proposed plant is to be built in two phases over seven years with a 1,000-megawatt first phase, according to The Climate Group. The organization reports that the first construction phase will cost $1.08 billion, and that the developers have approached the World Bank for a $500 million loan to begin the first 750 megawatts.

Fluor and the $22 Billion, 5-Gigawatt South African Project

Image: Artist's rendering of South African Solar Park, which includes PV and CSP technologies

A 317-page report on a proposed 5-gigawatt solar park in South Africa's Northern Cape Province was authored by EPC Fluor in 2011, along with a flurry of early feasibility studies for the country's Department of Energy. The Upington region was selected as a suitable site although it "does not have an established transmission network," according to the report. Few grids would be able to support this type of generation source without extensive transmission upgrades.

The South African government estimated the cost of the project at $22 billion in 2011. We've asked Fluor and the South African Department of Energy whether any progress has been made since then.

Desertec's Hundreds of Gigawatts

Desertec envisions a pan-African-Euro-MidEast grid powered by hundreds of gigawatts of centralized PV, CSP, wind and other renewables. The nonprofit foundation accepts PayPal if you're keen on donating -- which is in itself an indication of how the project is progressing.

Centralized or Distributed?

In the U.S., huge centralized generation projects are more difficult to finance, permit and integrate into the grid compared to smaller distributed generation projects. Regulatory and political headwinds also stall giga-scale projects.

But what about India or North Africa? Should these regions move their capital into giga-scale projects or point capital to distributed generation and grid edge solar?

"We have singularly failed in providing access to adequate, affordable and clean energy to a large section of the country’s population. As per the 2011 Census, one-third of households -- about 400 million people -- do not have access to electricity. In rural India, about 45 percent of households -- more than 77 million -- continue to use kerosene to light their homes and shops. With no access to any source of lighting, 1.2 million households go dark after sunset. The country is paying huge development costs because of this energy poverty. Education, health and economic development are getting stymied."

Bhushan asked: "In such a scenario, should we invest in large and expensive solar power plants that will feed electricity into a leaking grid (the T&D loss in the country was 24 percent in 2011-12) and provide subsidized solar electricity to the rich domestic, commercial and industrial consumers? Or should we invest in small solar power plants and local (mini) grids that can provide electricity to the energy poor?"

While these projects sit on the shelf waiting to get developed, people in need of electricity are getting served by a growing roster of off-grid solar companies. Will that trend continue? Or can the mega-plant ever win?

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Prior to joining Greentech Media, Eric Wesoff founded Sage Marketing Partners in 2000 to provide sales and marketing-consulting services to venture-capital firms and their portfolio companies in the alternative energy and telecommunications sectors. Mr. Wesoff has become a well-known, respected authority and speaker in these fields. He also was the publisher of the Venture Power newsletter, a ...

Centralized generation requires more electrical lines and higher losses traveling long distances. Decentralized generation can be placed right at the source where it is needed. This saves on the sizing of transformers and other sizing of electrcal distribution systems.

A lot depends on the location and regulatory framework of the country.

For example in the UK, the installed cost of utility scale solar is not very different to medium scale commercial rooftop such as 100kW - 1MW on a warehouse complex - in fact, in some cases, the rooftop array may produce power at lower cost.

Why?

Because the physical installed cost is only slightly different, and UK soft costs are fairly low - especially for rooftop arrays. (Ground mount are more likely to face planning difficulties, have additional land related costs, and also achieve lower value of electricity as ground mount solar farms generally have little of no self consumption). There is also a significant cost of connecting large ground mount projects to the grid whereas an industrial estate is already connected to the grid and needs no additional grid capacity to allow a roof mounted solar array.

In the USA, with much higher administrative soft costs, the difference is greater so tending to drive a higher proportion of large scale projects.

In the context of India, solar makes perfect sence for both on and off grid applications.

On grid, solar in India will produce the most power when air conditioning and commercial loads are highest - helping most when load would otherwise be shed (rolling scheduled power cuts). Solar is already very cost effective in India for commercial rooftop applications without subsidy - especially in areas where such businesses typically run for hours each day using costly on site diesel generators - with solar on site generation costing possibly half the cost of the diesel generator, and getting cheeper year by year.

Off grid, the capital cost of a complete small system of 10W to 20W PV for lighting and phone charging is far less than a year's supply of fuel for kerosine lights and has major advantages in terms of indoor and outdoor air pollution, health, and improved safety.

How much economy of scale is there in solar PV if the scale is pushed to the range of GWs? Any good references on this?

I would imagine that solar PV, being highly modular in nature, would reach optimal economics in the range of 10s or perhaps 100s of MW. Beyond that it could even start to become more expensive per Watt again. Concentrating such a large amount of PV in one location will enhance variability caused by clouds. Solar projects of such scale could also result in higher financing costs due to greater perceived risk.

Of course the difference is that one cloud can turn-off many GWatts of solar, but the nuclear park would fail 1 GWatt or so at a time, and of course the nuclear plants averages 4 times more annual output for the same nameplate capacity. So whatever the total regional solar generation, it is better that the biggest chunk is no more a few percent of the total grid capacity from all sources (India's total grid is currently 203 GWatts). 200 MWatt solar chunks are plenty big enough to capture economies of scale on the plant and transmission (most of India's existing nuclear reactors are 200MW, with new 630 MW domestically designed units under construction now).

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Centralized or distributed? Utility scale solar plants make energy for half the cost of residential rooftop, and have the further benefit of lowering the up-front cost of home ownership. Enough said.

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Is $1.1/Watt for India's Ultra Mega Solar project a good price? By US standards yes, but not in India (at 25% capacity factor, that's $4.4 per average Watt, even before any energy storage is added). India is currently building nuclear plants for $1.7/Watt (see here), which should reach 90% capacity factor now that they are allowed to import fuel (they'll also startup their first 500MW fast breeder this year, which will eventually eliminate the need to import fuel).

Someone should look at these numbers very, very, very, very carefully, in light of the fact that India is a country - I've seen it with my own eyes - that has a huge population of impoverished people.

How can one morally justify spending a billion dollars on a technology - which as advertised in terms of peak power, at "1000 MW" rather than actually continuous average power - that is the equivalent of a small gas plant, at best a 200 MW continuously operating power plant of any type?

I'm being generous with the 200 MW figure, since the number of solar facilities that operate as high as 20% capacity utilization is vanishingly small.

This is the moralproblem with the solar industry: It advertises itself dishonestly, covering up the huge associated costs, by continuously advertising peak power as average power.

In a sensible world this boondoggle wouldn't be built at all.

The irony of this post - and I'm sure it's unintentional - is that it refers to Indian homes that go dark at night because there's no electricity. What's the capacity utilization of a solar plant at night, and how can a solar plant be expected to address the problem of the lack of electricity for lighting?

Maybe we can imagine a solar/light perpetual motion machine? Another billion bucks for batteries?

India has demonstrated repeatedly that it can build a nuclear plant for under 4 billion dollars. I can't imagine why anyone in that country would imagine building anything else for that kind of money. A nuclear power plant will last long longer, work better, produce less environmental destruction, and save more lives and raise the living standards of more people.